Exciting Captures and Observations:

December was a very exciting month for the banders with new species encountered and high capture rates at our “offsites” (mist-netting sites around West Marin County).

Rare bird alert! We captured a Swainson’s Thrush at Pine Gulch in the Bolinas Lagoon Open Space Preserve on December 21st! Their close cousin, the Hermit Thrush, is a common wintering species in Marin County, however the Swainson’s Thrush is a long distance migrant whose winter range extends from Mexico into South America. Swainson’s Thrushes are common here in the breeding season but are typically all off to their winter grounds by October. This capture is particularly interesting to the greater Point Blue community, considering that this is the latest date we have ever captured this species in Palomarin’s 51 year history!

Left: Hermit Thrush; Right: Swainson’s Thrush. We use wing morphology to distinguish between these two thrush species. Notice that the Swainson’s Thrush wing is more elongated than the Hermit Thrush. Photo by Krista Fanucchi

We were also thrilled to capture so many Yellow-rumped Warblers at our offsites this month. We catch both the Myrtle’s and Audubon’s subspecies of Yellow-rumped Warbler here in West Marin which are distinguished by different facial patterns and the presence or absence of yellow in their throat. We look at other plumage characteristics of the Yellow-rumped Warblers that we catch to try to determine their age and sex, though this often proves to be quite difficult.

Audubon’s Warbler. Photo by Hilary Allen

On the winter solstice we captured a Gambel’s White-crowned Sparrow (Z. l. gambelii) at one of our west Marin off sites. In North America we have five subspecies of White-crowned Sparrows. The Nuttall’s White-crowned Sparrow (Z. l. nuttalli) is a non-migratory subspecies that occurs here in Marin County year-round. In the fall and winter we capture other migrant subspecies, most commonly the Puget Sound White-crowned Sparrow (Z. l. pugetensis) which winters along the coast from southern Washington to southern California. The Gambel’s subspecies usually winters further east from here, making this an unusual and exciting capture!

Gambel’s White-crowned Sparrow. Photo by Hilary Allen

We caught two species of woodpecker in December. A Downy Woodpecker at Pine Gulch on December 12th and a Hairy Woodpecker at the Palomarin Field Station on December 24th.

Left: Hairy Woodpecker; Right: Downy Woodpecker. These two species have a very similar appearance, but the Downy Woodpecker is significantly smaller. Photos by Kimberly Navarro-Vélez and Krista Fanucchi

Our last two birds captured and banded in 2017 were a Hutton’s Vireo and a Ruby-crowned Kinglet, which are very similar in appearance and often misidentified in the field. Examine the picture below, can you tell which one is which?

Let’s Do the Numbers:

In 16 days (1764.55 net hours) of mist-netting at Palomarin in December, we captured 40 new birds and recaptured 74 previously banded birds. A total of 114 birds of 18 species were caught. Approximately 7 birds were caught per banding day.

At our other West Marin banding sites, we captured 124 new birds and recaptured 74 previously banded birds. A total of 198 birds of 23 species were caught over 8 banding days in December (451 net hours), an average of approximately 24 birds per day.

The highest capture rates at Palomarin and our other West Marin banding sites were on December 2nd at Palomarin with 12 birds and December 21st at Pine Gulch with 62 birds.

About these Summaries:

In an effort to share our science with the public, Point Blue interns and staff at our Palomarin Field Station (Palomarin or “Palo”) in Point Reyes National Seashore near Bolinas, CA produce these monthly bird-banding summaries. Our science interns create these summaries as part of their science outreach training.

About this blog

Operating since 1966 in partnership with the Point Reyes National Seashore, Point Blue's Palomarin Field Station is one of the premier locations nationally for long-term studies on birds and their habitats and training the next generation of conservation scientists. With information collected at this field station, we guide conservation action to reduce the negative impacts of habitat degradation, climate change and other environmental stresses on birds, other wildlife and our communities.

On this blog you will find monthly bird-banding summaries compiled by our conservation science interns, the occasional Throwback Thursday, and entries from our scientists, educators, and interns about research and conservation work being done at the Palomarin Field Station.